Georgia Power has returned to the Atlanta Gas Light Site to remove 4000
cubic yards of soil approximately 30-40 feet underground. The Site was
extensively cleaned up in 2000 and the expectations were that the residual
groundwater contamination would decrease to drinking water standards. Even
though contaminants in water did come down and the area shrunk considerably,
drinking water standards were not being met.

An investigation of the area causing the problem revealed some tar like
substance had leaked deep into the ground and was the source of the
contamination. Unlike water, the liquid like source of the problem moved as
a Dense Non-Aqueous Phase Liquid (see diagram below) and follows the path of
least resistance. Often, this is the hardest type of contamination to
track since it can move down, then sideways, and down again.

The goal of the current removal action is to remove all the soil that could
possibly contain these ribbons of tar like material sitting deep underground
and below the water table. The wet soil will be placed on a dewatering pad,
the water collected, and the soil removed from the Site. In place of the
soil, a Portland cement and bentonite (clay) mixture will fill the
excavation.

The entire project is expected to take between 3 and 4 months to complete,
followed by groundwater monitoring to assess success of the removal.

Skip
Rickerson, On-site Project Manager, stands next to one of the six air
monitoring stations set up at the Site.

Crews
install the dewatering pad and prepare to pour cement for the
decontamination pad for trucks leaving the Site.

Dense
Non-Aqueous Phase Liquids (DNAPL) act differently than water, can travel
deep into the ground,
and contaminate water for a long time.